Japanese Patent Laying-Open No. 2010-239791 (PTL 1) discloses a technique of setting, as a limit voltage, a voltage that tends to decrease as the atmospheric pressure becomes smaller (the altitude becomes higher), and using the set limit voltage to set a target voltage to be supplied to an inverter, thereby controlling a boost converter. According to this technique, even if the withstand voltage of loading components such as an electric motor is decreased due to a relative low atmospheric pressure, it becomes possible to prevent a dielectric breakdown from occurring in these loading components such as an electric motor.